This invention relates generally to a track chain for use on earthmoving machines, and more particularly to a method and apparatus for retaining the joints of the track chain.
A track joint is usually held together by an interference fit between the ends of the track pins and their respective link bores into which the pin ends are tightly received. Even though a very high press force is used to press the links onto their respective pin ends, the links still have a tendency to move outwardly on the pin as a result of working forces exerted on the track during operation of the machine. This outward movement causes the joints to become loose or develop what is commonly referred to as end play.
Various methods have been tried to limit the amount of end play in track joints. Keeper assembles, such as those disclosed in U.S. Pat. No. 4,182,578 issued on Jan. 8, 1980 and U.S. Pat. No. 4,288,172 issued on Sep. 8, 1981, both to Richard Livesay et al. And both assigned to the assignee hereof, have been successfully employed to reduce such end play movement. In order to accommodate manufacturing tolerances, joints utilizing such keepers must have a certain amount of clearance which produces a limited amount of built-in end play. As a result, these keepers reduce, but do not completely eliminate end play.
Another method of limiting end play is disclosed in U.S. Pat. No. 3,831,257 issued on Aug. 27, 1974, to Roger L. Boggs et al., which patent is also assigned to the assignee hereof, wherein welding about the ends of the track pin is used. In this method, retention is dependent on the strength of the weld. In practice, weld strength is difficult to control with any degree of consistency. If a weld is so weld that it breaks, all of its retention ability is lost.
More recently, the method and apparatus for retaining a track joint disclosed in U.S. Pat. No. 5,201,171, issued on Apr. 13, 1993, to Peter Anderton et al. And also assigned to the assignee hereof, has been successfully utilized. In such apparatus and method, an appropriate groove must be machined in the pin and material from the boss is displaced in the radial direction into the groove of the pin.
The solution to the above problems is hampered by another problem, which is inability to change dimensions of the track. One such dimension is the rail-to-rail width or gauge of the track. Like railroad track, the track links provide a pair of rail surfaces on which the wheels or rollers of the machine ride. The rail width or gauge for any particular machine is, for all practical purposes, permanently set and cannot be changed. This is because any change in rail gauge would require corresponding changes in the remaining components of the machine undercarriage and because the changed track would not be interchangeable with the track of existing machines.
The present invention is directed to overcoming the shortcomings of the prior attempts at providing a track joint with restricted end play.
In one aspect of the present invention, there is provided a method of assembling a joint of an endless track chain for track type machines to prevent end play in the joint. The joint includes a pair of links and a cylindrical pin. Each link includes a laterally outwardly offset outboard end collar having a boss extending outwardly therefrom and a bore therethrough each boss having a side surface. The pin includes opposite end portions, each end portion being non-rotatably mounted into a respective one of the bores of the outboard end collars. The method comprising the steps of forming a annular groove about each of the end portions of the pin, placing a swag tool against the side surface of the boss in axial alignment with the pin, applying a sufficient force on the swag tool to form at least one mechanically formed nodule protruding from the side surface of the boss into respective one of the grooves of the pin, the nodule having a cross-sectional configuration substantially conforming to the groove.
In accordance with another aspect of the present invention, an apparatus for retaining the track joints of an endless track chain for a track-type machine is provided to prevent end play in the joints. Each joint includes a pair of links and a cylindrical pin. Each link has an outboard end collar with a pin boss extending outwardly therefrom and a bore therethrough. The pin boss has a side surface. Each pin has opposite end portions, each end portion being pressed and non-rotatably mounted into a respective one of the bores of the outboard end collars. The apparatus comprising an annular groove formed in each of the opposite end portions of the pin. Each groove is disposed within the bore at a location along the pin boss. At least one mechanically formed nodule protrudes from the side surface of the pin boss into respective ones of the pin grooves. Each nodule has a cross-sectional configuration substantially conforming to its groove and is formed from material that has been permanently extruded from the side surface of the pin boss into the groove.